I've always found Jesus' remark in Luke 17:6 fascinating. He said that, "If you have faith as small as a mustard seed, you can say to this mulberry tree, 'Be uprooted and planted in the sea,' and it will obey you."
This, of course, sounds like a very useful thing, especially if you are in the tree removal business, but despite an experimental prayer - experimental since I don't really need any trees moved into the ocean - the tree I prayed for remained in place. And a very good thing, on reflection, since is was not my tree I was praying about. Bad me.
But anyway, then I was discouraged. Clearly I didn't even have that tiny bit of faith Jesus says is necessary to move trees.
But when I went back and read the passage more carefully I found I was foolishly adding something that didn't belong. I was incorrectly understanding the passage to say: "Work hard building up your faith and someday when it's really strong then you can use it to uproot mulberry trees."
As I understand it now, Jesus wasn't telling the apostles that they needed more faith, but was simply saying what he said, that if you have enough faith then the tree will move. And if you don't, it won't. There may be cases when God gives you enough faith that your prayer will be answered with a miracle; in other cases he will not give you that level of faith. So relax (I'm talking to myself especially) and don't try to juice up your faith by furrowing your eyebrows and squinting really hard.